Rotary positive displacement unit

ABSTRACT

The units contain pairs of toothed intermeshing members running on axes that intersect at an angle differing from 180* by half the tooth-height angle. Their tooth numbers differ by one. Ducts lead fluid to and from the intermeshing members. In units containing two of said pairs their larger members are coaxial and form a rigid rotor. The invention gears this rotor directly to the outside, without driving through the smaller member of one pair. It thereby minimizes the load transmitted through the tooth sides of each pair. The shaft geared to said rotor is positioned to minimize the bearing loads thereof. Generally the shaft axis lies in an axial plane of said rotor inclined to the plane of the axes of each of said pairs. The improvement further resides in the mounting of the smaller member of a pair and in the shape of the duct openings at the intermeshing members.

United States Patent [191 Wildhaber June 18, 1974 [57] ABSTRACT Theunits contain pairs of toothed intermeshing members running on axes thatintersect at an angle differing from 180 by half the tooth-height angle.Their tooth numbers difier by one. Ducts lead fluid to and from theintermeshing members. In units containing two of said pairs their largermembers are coaxial and form a rigid rotor. The invention gears thisrotor directly to the outside, without driving through the smallermember of one pair. 1t thereby minimizes the load transmitted throughthe tooth sides of each pair.

The shaft geared to said rotor is positioned to minimize the bearingloads thereof. Generally the shaft axis lies in an axial plane of saidrotor inclined to the plane of the axes of each. of said pairs. Theimprovement further resides in the mounting of the smaller member of apair and in the shape of the duct openings at the intermeshing members.

9 Claims, 8 Drawing Figures ROTARY POSITIVE DISPLACEMENT UNIT [76]Inventor: Ernest Wildhaber, 124 Summit Dr.,

Brighton, NY. 14620 [22] Filed: Feb. 12, 1973 [21] Appl. No.: 331,781

[52] US. Cl 418/195, 418/200, 60/396] [51] Int. Cl. FOlc l/08, F03c3/00, F04c 17/04 [58] Field of Search 418/9, 10, 194, 195, 199, 418/200;60/3945, 39.61, 39.63 [56] References Cited UNITED STATES PATENTS739,207 9/1903 Nielsen 418/195 1,912,634 6/1933 Gray 418/193 3,207,1379/1965 Lanahan 418/195 3,236,186 2/1966 Wildhaber 418/193 3,273,3419/1966 Wildhaber 60/3961 3,433,167 3/1969 Craig 418/195 3,442,181 5/1969Olderaan 91/500 3,492,974 2/1970 Kreimeyer 418/68 PrimaryExaminer-Carlton R. Croyle Assistant Examiner-John .1. V rablik v 76 9!9o: as if PATENTEMuu-r a an aianlsse SHEEI 30$] 3 ROTARY POSITIVEDISPLACEMENT UNIT This is an improvement on my US. Pat. Nos. 3,236,186and 3,273,341 granted in 1966. The invention can be embodied as acompressor for air or gases, as an engine for compressed air, steam, orhot combustion gases, as a pump or motor for liquids, and particularlyas a rotary positive displacement unit containing two pairs ofintermeshing toothed members. The two pairs may be used in parallel orin series, as for instance one pair compressing air and the otherletting it expand after or during combustion, to provide an engine.

For the last-named case a unit has been proposed wherein the enginepower is transmitted to the outside through the smaller member of itspair. This results in an ample amount of torque transmitted through thetooth sides of the engine pair.

One object of the present invention is to drastically reduce thistorque. A further object is to then do away with liquid lubrication ofthe tooth surfaces or to much reduce it.

A further aim is to provide a unit with two pairs of rotary memberswherein the gear drive is placed to produce minimum bearing loads. Afurther object is an improved mounting of the smaller member of thepair. A still other aim is to reduce leakage by improving the shape andposition of the fluid ducts where they reach the intermeshing pair ofmembers.

Other objects will appear in the course of the specification and in therecital of the appended claims.

The invention will be described with reference to the drawings in whichFIG. 1 is a side view of a pair of toothed intermeshing members used inthe invention, the view being taken at right angles to the plane oftheir intersecting axes.

FIG. 2 is a development into a plane of what might be called the backcone of the smaller member, illustrating the contact of its tooth ends.It represents the intersection with the extended teeth, of a conecoaxial with said member and tangent to the spherical outside surface.

FIG. 3 is a fragmentary view of the intermeshing teeth, taken radiallyalong the line of contact of the conical pitch surfaces.

FIG. 4 is a radial view along the plane of the axes taken at thediametrically opposite side of the intermeshing members.

F IG. 5 is an axial section of a compressor showing the improvedmounting of the smaller member.

FIG. 6 is an axial section of a unit containing two pairs ofintermeshing members. It applies for instance to a pair of compressors.

FIG. 7 is a diagram showing the position of the gears with respect tothe plane of the axes of the pairs.

FIG. 8 is an axial section of a unit containing a compressor pair and anengine pair of members, constructed according to the invention.

FIG. 8a is a repetition of FIG. 8, showing added to it a combustionchamber 98 and passages 96, 99 to and from it.

The intermeshing rotary members 11, 12 (FIG. 1) turn on axes 11', 12'that intersect at 0. They have tooth numbers differing by one. Thesmaller member 12 may have n teeth and the larger member 11 may have (nl) teeth. The teeth are tapered. They extend between a conical facesurface and a conical root surface having a common apex at 0, best seenin axial section FIG. 5. The angle 14 between the axes 11, 12' differsfrom degrees by half the angular height 15 of the teeth 16, 17, so thatthe teeth may remain in contact with one another along the entirecircumference of the members. The tooth shape has been described atlength in the aforesaid patents.

In one procedure the outside end-surface 18 of the teeth 17 of thesmaller member 12 is assumed, for instance as a conical surface withapex at 0. The entire tooth surface of the larger member is then formedconjugate to said end surface 18, so that end-surface 18 completelyenvelops it when member 12 turns in engagement with member 11 at theratio n l/n of the tooth numbers at the angular setting of the finalpair. This results in a path of contact 20 between the tooth tops 18 andthe teeth 16. It is shown in dotted lines in FIGS. 1 to 3.

The complete tooth shape of the smaller member 12 is formed conjugate tothe just defined tooth shape of the larger member 11. This results in afurther path of contact 21, 21' between the tooth sides, (FIG. 3). Themating tooth sides have little relative curvature. They hug each other,so that the surface stresses at the contact remain low.

While gears with parallel axes, an external gear and an internal gearwith one more tooth, are restricted to a tooth depth of one module, thatis to the circular pitch divided by 11', (11 3.1416), such restrictiondoes not apply to the design with intersecting axes. A tooth depth ortooth height of 2 /2 module or more may be provided. This avoids theexcessive inclination of the tooth sides of parallelaxes gears andprovides a sufficient duration of contact between the tooth sidesthemselves, along path 21 and 21'.

This is clearly shown in FIG. 3.

Seals are formed by tangential contact at the contact points of thetooth tops 18. These seals extend all around the periphery of themembers. Further seals are formed at the contact points, such as 23, 23'(FIG. 3), of the paths of contact 21, 21' between the tooth sides. Theselatter seals are however confined to the region of deepest penetrationof the members, where they have little effect.

The teeth of the two members leave spaces between them. Space 25, FIG.4, has the maximum volume. It is sealed at 24, 24'. The volumes diminisharound the periphery of the pair. Thus volume 26, (FIGS. 1, 2), sealedat 26 26', is slightly smaller. And volumes 27, 28, 29 are progressivelysmaller until they almost disappear in the region of deepestpenetration, (FIG. 3). Their seals are respectively at 26', 27; 27', 28;28, 29.

In a compressor, when members 11, 12 rotate in the direction of arrows30, 31, air or fluid filling space 25 is progressively transformed tovolumes 26, 27, 28, where it may get within reach of the outlet opening.Air or fluid is admitted while the penetration of the two membersdecreases, between the positions shown in FIGS. 3 and 4.

In an engine or motor fluid under pressure is admitted to spaces 29 andpossibly 28, when members 1 1, l2 rotate in directions opposite toarrows 30, 31. It expands as it reaches volume 27, 26, 25, and leavesthe intermeshing members during their increasing penetration, whichlasts through about half a turn.

When the unit is embodied as a pump for liquids, the exhaust ducts startand the intake ducts end near the location shown in FIG. 4.

In FIG. 1 dotted lines indicate the shape of the compressor outlet duct32, as it leaves the sphericaloutside surface of the pair 11, 12. Toavoid or restrict leakage as the members turn, one side 32 of the ductopening approximately follows the path of contact 20 of the tooth tops18 for a stretch adjacent the end furthest away from the plane of theaxes ll, 12. Considerable departure is permitted without materiallyaffecting the action, while keeping at a distance from the root surfaceof the smaller member. The other side 32 follows the root surface of thelarger member 11. The duct opening widens as it approaches the plane ofthe axes 11', 12'.

An intake duct opening of larger length is provided on the opposite sideof said plane.

In an engine or motor using compressible fluid, duct 32 is the inlet andthe longer duct opening on the opposite side the exhaust, provided thatthe members rotate in directions opposite to arrows 30, 31.

The longer opening, the intake on a compressor, is less critical. Oneend of this opening 34 is indicated in dotted lines in FIG. 4.

The ends of both openings adjacent pitch point 35, FIG. 3, are separateda moderate distance, (not shown).

It will now be demonstrated that the fluid pressure exerts practicallyno turning moment on the smaller member. Fluid in compartment 26, (FIGS.1 and 2), exerts a pressure whose resultant force is perpendicular tothe straight connecting line of the sealing points 26 26', andperpendicular to the plane through apex 0 of which this line is a part.It acts midway between the seals and is the product of the area in saidplane and the pressure per unit area.

Inasmuch as line 26 -26 extends almost peripherally, the resultant forcehas a very small distance from the turning axis 12 and exerts only asmall turning moment on member 12. It is opposed to the direction 31 ofits rotation.

The forces resulting from fluid pressure in compartments 27, 28, 29 areperpendicular respectively to the connecting lines 2627, 2728, 28-29 andare determined as described for compartment 26. The forces ofcompartments 27, 28 almost intersect the axis 12 and thus exert verylittle turning moment.

The resultant force of compartment 29 bypasses the axis 12' on theopposite side as compared with the one of compartment 26, and exerts aturning moment in the direction of rotation. Because of the largerpressure in compartment 29, it more than balances the opposite turningmoment. It may just about overcome the frictional resistance, so thatmember 12 floats freely about its axis.

By not driving through the smaller member, the tooth loads of themembers are minimized. The inventiontakes advantage of this particularlyin units containing two pairs of members.

FIG. illustrates an improvement in the mounting of the smaller member,whose axis 12 intersects axis 11 of member 1 1 at 0. Member 12 ofcompressor 40 is rotatably mounted on a spherical projection 41 rigidwith member 11 and further in a region spaced therefrom. The furtheraway from 0 this region is, the larger is the load carried by projection41. Because of its considerable slant and its moderate load-carryingarea it is desirable to keep its load down. The invention does this,using an external portion 42 rigid with the housing 43 and projectingtowards said intersection point 0 to the inside of the smaller member12. Projection 42 carries an antifriction bearing 44 capable of carryingcombined radial and axial load.

If desired, sliding bearings may be used instead, as at 45, 46 in FIGS.6 and 8. Their projecting portion is preferably tapered, decreasing indiameter towards 0.

The bearings 44, 45, 46 are preferably designed to carry nearly thetotal bearing load needed to rotatably mount the smaller member. Ifneeded, the direction of the bearing load can be influenced by exposingmore of the spherical outside surface of the member to the compressedfluid.

The larger member 11 is secured to a flange 19 of the part that alsocontains the spherical projection 41 and a shaft portion. It may besecured in any suitable known way, for instance by bonding.

FIG. 6 shows a twin compressor constructed accord ing to the invention.It is made up of two identical compressors 50, 50" to double the output.They contain intermeshing members 51', 52' and 51", 52 respectively. Themembers are shaped like the described members 11, 12.

The larger members 51, 51" are coaxial and rigidly connected with eachother by shaft portions 53', 53" and a toothed face coupling 54. Rigidengagement is maintained by a bolt 55 and nut 56, to form a rigid rotor.A cylindrical pinion 57 is secured to one of said shaft portions.Bearings 58, 59 mount this rotor assembly.

The axes of all rotating members 51', 52; 51", 52" lie in a commonplane. Pinion 57 meshes with a gear 57'. Its axis 60 is parallel to therotor axis 61 and thus lies in an axial plane of the rotor. This planeincludes an angle with said common plane, the drawing plane of FIG. 6.In accordance with the invention this angle is so determined as tominimize the loads on bearings 58, 59.

Diagram FIG. 7 is a view taken along the axis 61 of said rotor. Circle62 represents the outline of its members 51', 51". The drawing planecoincides with their mid-plane 63. The said common plane 64 of the axesappears vertical in FIG. 7.

With rotation in direction of arrow 65 the fluid pres sure creates aforce 66, on a compressor. This vector is inclined to the mid-plane andintersects it at 67. The forces exerted on the two members 51', 51" aresymmetrical to the mid-plane, like the members themselves. Their thrustcomponents along axis 61 are equal and opposite. They balance eachother. However their components in the mid-plane add to each other andhave the direction of the projected vector 66.

The pitch circle 57 of pinion 57 intersects the projected vector 66 at68. If the axis of the mating gear 57 lies on line 61-68, the tooth loadexerted on pinion 57 by gear 57' is inclined to its pitch circle 72.This load has to produce a turning moment equal and opposite to thatproduced by projected vector 66 of both members 51', 51": The peripheralload components are equal. If 68-68 is the force along projected vector66, 68-68" is a measure of the force along the tooth normal. Distance68'-68" is parallel to center line 60'-6l and is a measure of theresulting bearing load. It is small.

A still smaller bearing load is attainable when the axis of gear 57' isdisplaced about axis 61 to a position 60, through an angle 60'-61-60equal to the angle 68-68-68".

In the actual design the plane 60-61 or 60-61 may be kept horizontal. Inother words the gear axis is turned up to 60, while the common plane ofthe member axes is tilted to 64,. In FIG. 6 gear 57' is turned up intothe drawing plane and shown in dotted lines.

The stationary housing comprises end parts 74, 74"

and a center part 75, all rigidly secured together. The housing hasprojections for securing it to a base or frame. Outlet and inletchannels are shown in dotted lines only on the end part to the right, asthey do not appear directly in this sectional view. Their opening asthey meet the spherical outside surface of the intermeshing members hasbeen described with FIG. 1. The ducts otherwise are conventional and arenot further shown.

Conventional cooling means may be provided but are not shown. Theyinclude fins or channels for liquid cooling.

FIG. 8 shows an application of the described toothed members to aninternal combustion unit. It comprises a compressor 76 with a largertoothed member 77 and a smaller one 78. It further comprises an engineor motor 79 with a larger toothed member 80 and a smaller one 81. Thepairs of members are as described with FIGS. 1 to 4. The larger members77, 80 are coaxially arranged and rigidly connected by means of atoothed face coupling 82 similar to coupling 54in FIG.

6. 83 denotes the axis of the resulting rotor, and 84, 85

are the axes of the smaller members 78, 81 respectively. The axes 84, 85are shown turned into the drawing plane, although the plane of axes 83,84 does not coincide with the plane of the axes 83, 85, as will befurther described.

The rotor is mounted on bearings 86, 87 in the housing composed of endparts 88, 88" and connecting part 88. A bevel gear 89 is rigidly securedto the rotor adjacent bearing 87 and motor 79, so that its rearwardaxial thrust is opposed to the axial thrust exerted on member 80 by thefluid pressure. The axial thrust of the compressor plus the axial thrustof gear 89 may then nearly balance the axial thrust of member 80.

Bevel gear 89 meshes with another bevel gear 90, shown in dotted lines,whose axis 9] lies in a plane perpendicular to the axis 83 of thecoaxial members 77, 80. It is also in a plane containing the axis 83 ofmembers 77, 80 which plane includes an angle with a plane containing thelast-named axis 83 and axis 84 or 85.

In operation, air is condensed in the compressor at left and channelledinto a combustion room, whence it is admitted to the motor at right.Combustion may be either completed in the combustion room, or startedthere and completed in the motor during expansion. The latter procedureresults in lower maximum temperatures. Channelling and combustion spacesare known art and are not shown in detail.

For best results an analysis similar to the one described with FIG. 7 ismade. The pressure-force vectors and their intersection with themid-plane are however individually determined for the two members 77 and80, starting out at first from a common plane with axes 83, 84, 85, andthen turning one of the axes 84, 85

about axis 83 to reduce the bearing load. Then the bevel gear 90 is setabout axis 83 to its most favorable position.

The bevel gears or the cylindrical gears may be used in either of theembodiments described with FIG. 6 and with FIG. 8. Furthermore hypoidgears may be used in place of the bevel gears.

What I claim is:

1. A rotary positive displacement unit comprising two pairs ofintermeshing toothed members having tooth numbers differing by one,

the axes of said members intersecting at an angle differing from by halfthe angular height of the teeth, so that the teeth may remain in contactwith one another along the entire circumference of said members,

a housing in which said members are rotatably mounted,

ducts for leading fluid to and from the intermeshing members,

the member with the larger tooth number of one pair being coaxial andrigid with the member with the larger tooth number of the other pair,

a shaft for transmitting power,

and an'operative connection between said shaft and said coaxial membersbypassing the smaller members of said pairs.

2. A rotary positive displacement unit according to claim 1, whereinsaid shaft lies in a plane perpendicular to said coaxial members, gearsprovide said operative connection.

3. A rotary positive displacement unit according to claim 1, whereinsaid shaft lies in a plane perpendicular to said coaxial members, saidoperative connection is a pair of bevel gears.

4. A rotary positive displacement unit according to claim 1, whereinsaid shaft is parallel to the axis of said coaxial members, saidoperative connection is a pair of cylindrical gears.

5. A rotary positive displacement unit according to claim 1, wherein oneof said two pairs of members is the moving part of an internalcombustion motor, the other pair is the moving part of an air compressorfor feeding compressed air into a combustion chamber and to said motor.

6. A rotary positive displacement unit according to claim 1, wherein theaxis of said shaft lies in a plane containing the axis of said largermembers, said plane includes an angle with a plane containing thelastnamed axis and the axis of at least one of the smaller members.

7. In a rotary positive displacement unit comprising at least one pairof intermeshing toothed members having tooth numbers differing by one,

the axes of said members intersecting at an angle differing from 180 byhalf the angular height of the teeth, so that the teeth may remain incontact with one another along the entire circumference of said members,

a housing in which said members are rotatably mounted,

ducts for leading fluid to and from the intermeshing members,

the smaller member of said pair being rotatably supported by a sphericalsurface portion concentric with the intersection point of said axes andrigid 8. In a rotary positive displacement unit the combinationaccording to claim 7, wherein the projecting portion is tapered,decreasing in diameter in a direction towards said intersection point.

9. In a rotary positive displacement unit the combination according toclaim 7, wherein the projecting portion contains an antifriction bearingcapable of taking combined radial and axial thrust load.

1. A rotary positive displacement unit comprising two pairs ofintermeshing toothed members having tooth numbers differing by one, theaxes of said members intersecting at an angle differing from 180* byhalf the angular height of the teeth, so that the teeth may remain incontact with one another along the entire circumference of said members,a housing in which said members are rotatably mounted, ducts for leadingfluid to and from the intermeshing members, the member with the largertooth number of one pair being coaxial and rigid with the member withthe larger tooth number of the other pair, a shaft for transmittingpower, and an operative connection between said shaft and said coaxialmembers bypassing the smaller members of said pairs.
 2. A rotarypositive displacement unit according to claim 1, wherein said shaft liesin a plane perpendicular to said coaxial members, gears provide saidoperative connection.
 3. A rotary positive displacement unit accordingto claim 1, wherein said shaft lies in a plane perpendicular to saidcoaxial members, said operative connection is a pair of bevel gears. 4.A rotAry positive displacement unit according to claim 1, wherein saidshaft is parallel to the axis of said coaxial members, said operativeconnection is a pair of cylindrical gears.
 5. A rotary positivedisplacement unit according to claim 1, wherein one of said two pairs ofmembers is the moving part of an internal combustion motor, the otherpair is the moving part of an air compressor for feeding compressed airinto a combustion chamber and to said motor.
 6. A rotary positivedisplacement unit according to claim 1, wherein the axis of said shaftlies in a plane containing the axis of said larger members, said planeincludes an angle with a plane containing the last-named axis and theaxis of at least one of the smaller members.
 7. In a rotary positivedisplacement unit comprising at least one pair of intermeshing toothedmembers having tooth numbers differing by one, the axes of said membersintersecting at an angle differing from 180* by half the angular heightof the teeth, so that the teeth may remain in contact with one anotheralong the entire circumference of said members, a housing in which saidmembers are rotatably mounted, ducts for leading fluid to and from theintermeshing members, the smaller member of said pair being rotatablysupported by a spherical surface portion concentric with theintersection point of said axes and rigid with the larger member of thepair and further by bearing contact at a region spaced therefrom to oneside only of said intersection point, the improvement wherein anexternal portion is rigid with and projects from the housing towardssaid intersection point to the inside of said smaller member to providesaid further contact, whereby to ease the contact at said sphericalsurface and to receive the major part of the bearing loads.
 8. In arotary positive displacement unit the combination according to claim 7,wherein the projecting portion is tapered, decreasing in diameter in adirection towards said intersection point.
 9. In a rotary positivedisplacement unit the combination according to claim 7, wherein theprojecting portion contains an antifriction bearing capable of takingcombined radial and axial thrust load.